Category Archives: Books and Resources

Book recommendations, reviews, notes, etc.

gerbv – A free, open source gerber viewer for Linux / OS X

When you finish a PCB design, you typically use the CAM export function of your layout tool to generate a set of gerber files to send to the PCB manufacturer.  To avoid errors in the finished board, it’s usually a good idea to review the files before you click send.

Enter gerbv, a free, open source gerber viewer that is available for many platforms, including Debian and OS X (via fink).

I recently upgraded to version 2.0 (I was using the really outdated version 1.0 on Macports) and I am really impressed by the improvements in the GUI and overall usability.

gerbv is a part of the gEDA suite, which also includes layout and schematic capture tools that are slowly becoming more popular vs. more established non-free tools like Eagle.

Update: I missed an interesting update to a post over on My 2uf, not everyone seems to like the rest of the gEDA suite.

gerbv screenshot
gerbv screenshot

Free IPC-7351 Land Pattern Calculator

Let’s say you are designing a printed circuit board in Eagle, and you need to place a component that you’ve never used before.  In Eagle, before you can use a new component, you need a land pattern, a schematic symbol, and a mapping between them to fully define the part.  Often, you can search through Eagle’s included libraries and find what you need (or something close enough).  But what if that fails?

The symbol and pin definitions are usually pretty easy – just copy the datasheet.  The hard part is the land pattern: the collection of copper traces, soldermask openings, silkscreen, and other features that define the part on the PCB.

To come up with a land pattern, you usually have a few options:

  1. Someone else may have done you a big favor by creating a part definition and uploading it to the Eagle library directoryCaveat: Use it at your own risk.  Surface mount parts tend to be particularly hard to use right out of the box – often someone else’s land pattern won’t even pass your DRC.  Whose process were they using, anyway??
  2. Look through the datasheet for the part to try and find a recommended land pattern. (Good luck!  Increasingly these are not included, but may be somewhere else on the manufacturer’s website.  Google is your friend!)
  3. Take a guess based on the geometry of the part, assuming you have a mechanical drawing or a physical sample somewhere.
  4. Skip 1-3 and use an IPC-7351 land pattern generator.

IPC-7351 is a standard for printed circuit board land pattern designs.  The standard attempts to, well, standardize land patterns to try to discourage every PCB designer from having his or her own custom library of land patterns.  IPC takes known good land patterns and combines them with accepted manufacturing tolerances to produce a land pattern that will work for most people most of the time.  Increasingly you will see references to IPC-7351 in datasheets instead of a land pattern drawing, so access to the standard is becoming more important over time.

Cool, right?  Well, the bad news is that while you can browse through the table of contents/introducton for free, downloading the standard costs big bucks.

Fortunately, PCB Matrix has a free IPC-7351 Land Pattern Calculator (direct download link here) that you can use to generate land patterns based on the standard.  You don’t need to own a copy of the standard to benefit from it.

The calculator is somewhat tricky to use but if you click the right buttons you can get something like what is shown below (click to enlarge).

Thin SOT23 8-pin Package Land Pattern Screenshot
PCB Matrix IPC-7351 Land Pattern Calculator Screenshot

X and Y are the dimensions of the recommended pads for an 8-lead Thin SOT-23, which happens to be the package for the LT3464.

With this information, you can return to Eagle and create a land pattern for your device.  PCB Matrix will also sell you premade Eagle libraries, but from their site it was not clear how much they cost.  Based on their other products, my guess is several hundred dollars and a yearly maintenance contract – I’ll draw my own, thanks.

Unfortunately, the calculator is Windows only, so Mac guys like me need to use VMware Fusion or similar to use it.  Can someone create a web version, please?

Merry Book-mas

This Christmas I received a bunch of great books from friends and family.  My O’Reilly collection in particular doubled in size!

Here’s a list of what I’ll be reading in 2009:

Programming and Customizing PICmicro Microcontrollers, by Myke Predko

Programming and Customizing PICmicro Microcontrollers

Programming & Customizing PICmicro Microcontrollers, by Myke Predko, is probably the best book out there for someone who is starting out with the PIC series of microcontrollers from Microchip.  I used Myke’s book as both a tutorial and reference when I created my PIC RGB Video Display.  Since then, I have referred back to this book countless times even when working with other microcontrollers, like Atmel’s AVR family, because it contains so much useful architecture-independent technical information.  I have referred to this book for information about topics including LCD interfacing, debouncing switches, RS-232 serial interfaces, and multiplexed LED drivers.  As a technical reference it easily surpasses the majority of AVR books that are out there.

The book is starting to show it’s age by not including some of the latest PIC micros in the examples (like the PIC16F628), but the code is easily ported to newer/faster/better microcontrollers, a good learning excercise in itself.

The greatest electronics book ever written?

Getting Started in Electrionics, by Forrest M. Mims, III

Getting Started in Electronics, by Forrest M. Mims, III. is a spectacular introduction to the world of electronics.  This book is not new – the truth is that it has changed little since it’s first release in 1983.  Despite this, twenty-five years later, there is really nothing else like it.  This book is suitable for beginners of any age yet it comprehensively describes the technical theory and practical use of electronic devices like resistors, capacitors, inductors, diodes, transistors, FETs (including the now-rare JFET), and LEDs, as well as circuits like amplifiers, oscillators, and logic gates.  There is even a graphical introduction to device physics (semiconductor materials, doping, electrons and holes) and semiconductor fabrication!  This is kind of stuff they teach third-year students in university ECE classes, written in a way that is understandable to a child in third grade!

The entire book is formatted like an engineering notebook with handwritten notes on every page.  The illustrations are fun and make the book friendly and accessible.    Here is an excerpt from the chapter on diodes:

Getting Started in Electrionics, by Forrest M. Mims, III

My father gave me this book when I was six or seven years old along with a 25 watt soldering iron from Radio Shack.  I am convinced that this book, together with a Science Fair 160-in-ONE kit, is what caused me to pursue a career in Electrical Engineering.  I still enjoy leafing through its pages and proving to myself that I can understand how each circuit works.

Forrest Mims himself is an interesting individual and has led a prolific career as a writer and amateur scientist.  He is an active member of the Society for Amateur Scientists (SAS) and edits the Citizen Scientist.

The book even includes a handy guide to help you learn How to Solder!

Getting Started in Electrionics, by Forrest M. Mims, III

Thankfully, it turns out that this fantastic book is still in print. The groovy green cover is gone (a mistake, in my opinion), but the contents have not changed.  This is fantastic news for anyone interested in learning about electronics.  These also make great Christmas presents – I bought one for my brother last year and he loved it!

In my opinion, this is probably the greatest introductory book about electronics ever written.  I’d be curious to hear if anyone has any other favorites – leave a comment if you do!

Happy 25th, Getting Started in Electronics!